environs: add NewEnviron(kind, config)

environs/interface.go

 package environs
 
 import (
         "errors"
         "io"
         "launchpad.net/juju/go/schema"
         "launchpad.net/juju/go/state"
 )
 
 // A EnvironProvider represents a computing and storage provider.
 type EnvironProvider interface {
         // ConfigChecker is used to check sections of the environments.yaml
         // file that specify this provider. The value passed to the Checker is
         // that returned from the yaml parse, of type schema.MapType.
         ConfigChecker() schema.Checker
 
-        // Open creates a new Environ with the attributes returned by·
-        // schema.Checker.Coerce(). The name is that given in environments.yaml.

[niemeyer, 2012/05/17 01:23:08]

There's a relationship between ConfigChecker and Open that was lost in the
rewrite. I suggest something like this:

// Open opens an environment with config, which must
// have been processed and validated by the schema
// checker returned by ConfigChecker.

Then, s/attributes/config/ below.

[dave_cheney.net, 2012/05/17 01:46:52]

Done.

-        Open(name string, attributes interface{}) (Environ, error)
+        // Open opens an environment with config, which must
+        // have been processed and validated by the schema
+        // checker returned by ConfigChecker.
+        Open(name string, config interface{}) (Environ, error)
 }
 
 var ErrNoDNSName = errors.New("DNS name not allocated")
 
 // Instance represents the provider-specific notion of a machine.
 type Instance interface {
         // Id returns a provider-generated identifier for the Instance.
         Id() string
 
         // DNSName returns the DNS name for the instance.
@@ skipping 67 matching lines @@
         RemoveFile(file string) error
 
         // Destroy shuts down all known machines and destroys the
         // rest of the environment. A list of instances known to
         // be part of the environment can be given with insts.
         // This is because recently started machines might not
         // yet be visible in the environment, so this method
         // can wait until they are.
         Destroy(insts []Instance) error
 }